The present invention relates generally to fire resistant construction materials and more particularly to a non-combustible joint packing product for preventing the spread of fire through a joint formed by adjacent building panels, and to the production and installation of such a joint packing product.
The use of prestressed, precast concrete panels, including curtain wall, in the construction of buildings is well known in the construction arts. Such panels may be used to clad the exterior walls of buildings and may also serve as portions of interior walls. In forming walls from such panels, the panels are spaced apart to allow for expansion and contraction. The width of the gap or joint between these wall panels is generally on the order of one-quarter inch to one inch.
It has been found that when one surface of a wall formed from such panels is exposed to fire, the capacity of the wall to withstand heat and to prevent the spread of fire to the area on the opposite side of the wall is largely dependant upon the type of material used to fill or seal off the joints between panels.
A problem encountered in joint preparation for resisting the penetration of heat and/or flames has been that during fire conditions an air pressure differential develops between the side of the wall exposed to the fire and the opposite side of the wall. The heat of the fire tends to shrink or burn away any sealant material provided at the surface of a joint and the pressure differential between the two sides of the wall tends to cause any other material which is positioned within the joint to be blown out of position or to be distorted, allowing the rapid passage of air and thus heat and/or flame from the fire side of the wall to the opposite side of the wall. Once such a flame passage through the joint is provided, fire and smoke spread quickly through the wall to the adjoining area, thus defeating the otherwise excellent fire resistant properties of prestressed, precast concrete and curtain wall panels.
In order to prevent the spread of fire through joints, various joint treatments have been utilized which provide a layer of blanket like fire resistant material which is supported in position by a polyethylene, closed-cell backup strip positioned adjacent to the fire proof blanket material or alternately positioned near the opposite wall surface of the joint in an attempt to stabilize the fire resistant blanket material within the joint. A problem with such a solution has been that the handling and installation of blanket material and a foam rod is relatively slow and labor intensive and thus considerably increases the cost of joint preparation.
Various materials and procedures for forming fire resistant joints are discussed in a publication of the Portland Cement Association entitled "Fire Tests of Joints Between Pre-Cast Concrete Wall Panels: Effects of Various Joint Treatments" by A. H. Gustarerro and M. S. Abrams, PCI Journal, September/October 1975, pages 44-64. This report indicates that it is known to treat a joint for fire prevention by placing a neoprene tube filled with ceramic fibers in a portion of the joint slightly recessed from one wall surface and to thereafter seal off the recess space between the neoprene tube and wall face with a joint sealing material such as polyoxide urethane sealant. A problem with the use of a neoprene tube filled with ceramic fibers is that neoprene has limited heat resistance and produces substantial smoke emission when it oxidizes. Another problem is that the placement of ceramic fiber into a tube is extremely slow and expensive and is therefore impractical in lengths of more than a few inches.
It is an object of the present invention to provide a method for preparing wall joints which results in a joint filling which remains in position and which prevents passage of heat and flame through a joint even after continued exposure to heat and/or flame at one side of a wall formed by concrete or other similar panels.
It is also an object of the invention to provide such a joint treatment wherein the joint treatment requires a relatively small amount of labor.
It is another object of the invention to provide such a joint treatment using relatively low cost, low density material.
It is a further object of the invention to provide a method for manufacturing such joint preparation material in a relatively low cost, relatively high speed operation.